1. Field of the Invention
The present invention generally relates to a method of controlling a transport system and, more particularly, to a method of controlling the transport system including a transport robot or manipulator having two manipulator arms that is generally used in the manufacture of semiconductor devices or liquid crystal displays.
2. Description of the Prior Art
In the transport system used for transporting works such as, for example, semiconductor wafers or liquid crystal substrates, a robot or manipulator having two manipulator arms is generally employed to increase the efficiency of transport of the works. An example of the prior art transport system utilizing the two-arm robot is shown in FIG. 7. Referring to FIG. 7, reference numeral 4 represents a load lock chamber for accommodating a stack of works, and reference numerals 5 to 8 represent processing chambers in which chemical vapor deposition and etching are carried out successively to the works. A transport robot or manipulator 10 is shown as positioned at a center region of the circle having respective portions occupied by the chambers 4 to 8 and includes a first manipulator arm AM1 and a second manipulator arm AM2. This transport robot 10 is controlled by a main controller 20 through first and second robot controllers 30 and 31 for controlling the respective first and second manipulator arms AM1 and AM2.
In the prior art transport system shown in FIG. 7, each work is removed from the load lock chamber 4 through a vacuum-side door and is then transported to any one of the processing chambers 5 to 8. The work which has been subjected to a predetermined process such as, for example, chemical vapor deposition, in the processing chamber is subsequently transported either to the next one of the processing chambers 5 to 8 for subsequent processing or back to the load lock chamber 4.
A circuit block diagram of each of the first and second robot controllers 30 and 31 shown in FIG. 7 is shown in FIG. 8, and the manner in which communications are exchanged among the controllers 20, 30 and 31 are diagrammatically shown in FIG. 9. As shown in FIG. 8, each of the first and second robot controllers 30 and 31 includes an input/output (I/0) circuit 30a or 31a for interfacing between the main controller 20 and the respective robot controller 30 or 31, and a transport control circuit 30b and 31b for feeding a servo-driver 30c or 31c with position information required to execute a transport command, said servo-driver 30c or 31c being operable in response to the position information to drive a motor for actuating the associated manipulator arm AM1 or AM2.
Let it be assumed that the transport system shown in FIGS. 7 and 8 is instructed to execute two commands 1 and 2, as shown in FIG. 9, to transport the work in the load lock chamber 4 to the processing chamber 6 and to transport the work in the processing chamber 7 to the processing chamber 5, respectively.
When the command 1 is to be executed, the main controller 20 transmits to the first robot controller 30 a first swivel instruction to swivel the first manipulator arm AM1 to a position aligned with the load lock chamber 4. In response to this first swivel instruction, the first robot controller 30 causes the first manipulator arm AM1 to be swivelled to the position aligned with the load lock chamber 4, followed by generation to the main controller 20 a first completion signal indicative of completion of the swivel of the first manipulator arm AM1 to the position aligned with the load lock chamber 4. After having received the first completion signal, the main controller 20 transmits to the first robot controller 30 a first removal instruction to cause the first manipulator arm AM1 to remove the work from the load lock chamber 4. The first robot controller 30 having received the first removal instruction causes the first manipulator arm AM 1 to remove the work from the load lock chamber 4 and then supplied the main controller 20 with a second completion signal indicative of completion of removal of the work from the load lock chamber 4.
In response to the second completion signal, the main controller 20 transmits to the first robot controller 30 a second swivel instruction to swivel the first manipulator arm AM1 to a position aligned with the processing chamber 6. The first robot controller 30 upon receipt of the second swivel instruction causes the first manipulator arm AM1 to be swivelled to a position aligned with the processing chamber 6 and subsequently supplies the main controller 20 with a third completion signal indicative of completion of swivel of the first manipulator arm AM1 to the position aligned with the processing chamber 6. Generation of this third completion signal from the first robot controller 30 takes place upon completion of swivel of the first manipulator arm AM1 to the position aligned with the processing chamber 6.
Upon receipt of the third completion signal, the main controller 20 supplies the first robot controller 30 with a first placement instruction to set the work carried by the first manipulator arm AM1 to the processing chamber 6. After the work has been set to the processing chamber 6, the first robot controller 30 generates a fourth completion signal to the main controller 20, informing the main controller 20 of completion of placement of the work in the processing chamber 6. In this way, the command 1 is executed completely.
The command 2 is executed in a manner substantially similar to that described above in connection with the command 1 with communications being exchanged between the main controller 20 and the second robot controller 31 as shown in a lower portion of FIG. 9, to thereby complete the required work handling.
As discussed above, in the prior art transport system, the main controller 20 is required to transmit detailed and specific instructions to any one of the first and second robot controllers 30 and 31 and, therefore, communication between the main controller 20 and any one of the first and second robot controller 30 and 31 tends to be complicated and time-consuming.